The invention concerns a hydrostatic penetration device for placing on and penetration of the seabed, comprising a housing with a top cover and a bottom cover, and a through-going vertical tool for penetration of the seabed. The invention also concerns tools for use with a hydrostatic penetration device, especially a sampler for core samples, where the tool is a sampler tube.
In addition to being able to be employed together with the said tools, the hydrostatic penetration device will also be able to be employed to drive a test probe down into the seabed, for measurement of, for example, temperature, mechanical resistance and electrical conductivity.
There are known in the prior art hydrostatic penetration devices in the form of samplers for core samples, e.g. of sediments on the seabed, designed in principle as percussion drill machines, these samplers being operated by the pressure difference between a low pressure chamber provided in the sampler and the ambient hydrostatic pressure. The standard known samplers of this type comprise a head to which the tool or the sampler tube is attached and is driven down into the seabed by a piston provided in a piston cylinder which can be connected to the surrounding water. When the stroke movement is completed, the cylinder is evacuated to the low pressure chamber, and the piston returns to the initial position, whereupon the cycle process is repeated. The weight of the sampler head acts in conjunction with the hydrostatic pressure in order to provide the energy required to perform the stroke movement or the drop stroke. Stability problems often arise with such known samplers when they are equipped with long sampler tubes, and there can also be problems in providing sufficient energy if long sampler tubes are employed.
In order to avoid the drawbacks with known hydrostatic samplers, it has therefore been proposed that the tool or the sampler tube should be through-going in the sampler's head or housing and that the sampler head or housing should be placed on the seabed.
U.S. Pat. No. 3,693,730 describes a sampler in which a housing with an electromagnetic vibrator is placed on the seabed. A through-going tube is driven by means of the vibrator down into the seabed, and a drawworks is used to move the vibrator along the pipe.